Current density and conductivity dependent electroporation of Escherichia coli C600.

Transformation and surviving of E. coli C600 have been evaluated in dependence on the electric field strength and current density by changing the conductivity of the bacteria suspension. In this context the impact of making bacteria electrocompetent and the addition of NaCl solution was examined. Transformation efficiency declines with increasing conductivity of the suspension. When washing bacteria differently, the transformation efficiency correlates with the number of survivors. In contrary, adding different concentrations of NaCl has no effect on the surviving of E. coli C600. In dependence on the electric field strength, the transformation efficiency shows no effect on changing the conductivity. Regarding the transformation efficiency in dependence of the current density, a clear shift of the transformation maximum was observed. For higher conductivities, higher current densities are needed to reach the transformation maximum.

Monitoring induced gene expression of single cells in a multilayer microchip.

We present a microfluidic system that facilitates long-term measurements of single cell response to external stimuli. The difficulty of addressing cells individually was overcome by using a two-layer microfluidic device. The top layer is designed for trapping and culturing of cells while the bottom layer is employed for supplying chemical compounds that can be transported towards the cells in defined concentrations and temporal sequences. A porous polyester membrane that supports transport and diffusion of compounds from below separates the microchannels of both layers. The performance and potential of the device are demonstrated using human embryonic kidney cells (HEK293) transfected with an inducible gene expression system. Expression of a fluorescent protein (ZsGreen1-DR) is observed while varying the concentration and exposure time of the inducer tetracycline. The study reveals the heterogeneous response of the cells as well as average responses of tens of cells that are analyzed in parallel. The microfluidic platform enables systematic studies under defined conditions and is a valuable tool for general single cell studies to obtain insights into mechanisms and kinetics that are not accessible by conventional macroscopic methods.

Functional analysis of an olfactory receptor in Drosophila melanogaster.

Fifty nine candidate olfactory receptor (Or) genes have recently been identified in Drosophila melanogaster, one of which is Or43a. In wild-type flies, Or43a is expressed at the distal edge of the third antennal segment in about 15 Or neurons. To identify ligands for the receptor we used the Gal4/UAS system to misexpress Or43a in the third antennal segment. Or43a mRNA expression in the antenna of transformed and wild-type flies was visualized by in situ hybridization with a digoxigenin-labeled probe. Electroantennogram recordings from transformed and wild-type flies were used to identify cyclohexanol, cyclohexanone, benzaldehyde, and benzyl alcohol as ligands for the Or43a. This in vivo analysis reveals functional properties of one member of the recently isolated Or family in Drosophila and will provide further insight into our understanding of olfactory coding.

Investigation of a correlation between monoamine oxidase B and catechol-O-methyltransferase activity in human blood cells.

Monoamine oxidase B (MAO-B) and catechol-O-methyltransferase (COMT) are pivotal enzymes in the catabolism of several neurotransmitters. MAO-B and COMT activity can be reliably measured in human platelets and erythrocytes, respectively. This study investigated whether a correlation exists between the activity of the two enzymes in a panel of 47 elderly subjects (age range 55-80 years). No correlation was apparent between the two activities (r(2)<0.01), which suggests that, genetically, they are determined independently. COMT activity in a panel of 163 subjects showed a bimodal distribution with a nadir at approximately 38 pmol/h/mg Hb.

Pharmacokinetics and pharmacodynamics of single and multiple doses of the MAO-B inhibitor lazabemide in healthy subjects.

AIMS: The objectives of this study were to assess the tolerability, pharmacokinetics and pharmacodynamics of the reversible monoamine oxidase B (MAO-B) inhibitor, lazabemide, in healthy subjects. METHODS: Single and multiple (1 week) twice daily oral doses (100-350 mg) of lazabemide were administered sequentially to five groups of six healthy male subjects in a placebo-controlled, double-blind design. Adverse events, vital signs, and clinical laboratory variables were recorded. Pharmacokinetic parameters of lazabemide were determined after single and multiple doses. Pharmacodynamics were assessed by determination of MAO-B activity in blood platelets and intravenous tyramine potentiation tests. RESULTS: Lazabemide was well tolerated at all dose levels, causing no clinically relevant changes in vital signs or laboratory parameters. Headache was the most frequent adverse event at higher doses. Lazabemide was rapidly absorbed and eliminated by mixed linear and non-linear pathway. Only minor accumulation occurred upon multiple dosing and steady-state plasma concentrations were achieved on the third day. Lazabemide caused a rapid and reversible inhibition of MAO-B activity in platelets. The twice daily dosing regimen resulted in complete inhibition at all dose levels. The duration of complete inhibition was dose-dependent and ranged from 16 h with 100 mg to 36 h with 350 mg. The sensitivity to i.v. tyramine did not change to a clinically relevant extent following single and multiple doses of lazabemide. CONCLUSIONS: The clinical pharmacology characteristics of lazabemide did not differ markedly after single and multiple oral doses. A dose regimen of lazebemide 100 mg twice daily is anticipated because it caused full and continuous MAO-B inhibition.

Synthesis and biochemical evaluation of N-(4-phenylthiazol-2-yl)benzenesulfonamides as high-affinity inhibitors of kynurenine 3-hydroxylase.

In this paper we describe the synthesis, structure-activity relationship (SAR), and biochemical characterization of N-(4-phenylthiazol-2-yl)benzenesulfonamides as inhibitors of kynurenine 3-hydroxylase. The compounds 3,4-dimethoxy-N-[4-(3-nitrophenyl)thiazol-2-yl]benzenesulfonamide 16 (IC50 = 37 nM, Ro-61-8048) and 4-amino-N-[4-[2-fluoro-5-(trifluoromethyl)phenyl]-thiazol-2-yl] benzenesulfonamide 20 (IC50 = 19 nM) were found to be high-affinity inhibitors of this enzyme in vitro. In addition, both compounds blocked rat and gerbil kynurenine 3-hydroxylase after oral administration, with ED50's in the 3-5 mumol/kg range in gerbil brain. In a microdialysis experiment in rats, 16 dose dependently increased kynurenic acid concentration in the extracellular hippocampal fluid. A dose of 100 mumol/kg po led to a 7.5-fold increase in kynurenic acid outflow. These new compounds should allow detailed investigation of the pathophysiological role of the kynurenine pathway after neuronal injury.

Pharmacokinetic-pharmacodynamic interactions between two selective monoamine oxidase inhibitors: moclobemide and selegiline.

The objectives of this study were to assess potential pharmacokinetic and pharmacodynamic interactions between moclobemide and selegiline. Two groups of 12 healthy male and female subjects were treated with 200 mg moclobemide or 5 mg selegiline b.i.d. for 16 days. On study day 8, the alternative active drug or placebo was added to the respective treatments. Concentration-time profiles of moclobemide and two of its main metabolites and 3,4-dihydrox/phenylglycol (DHPG, a norepinephrine metabolite), 5-hydroxy-indoleacetic acid (HIAA, a serotonin metabolite), and 3,4-dihydroxyphenylacetic acid (DOPAC, a dopamine metabolite) in plasma as well as MAO-B activity and serotonin concentration in platelets were determined at steady state during monotreatment and combined treatment. The pharmacokinetic parameters of moclobemide and its metabolites changed on multiple dosing but were not influenced to a relevant extent by concomitant administration of selegiline. The measured pharmacodynamic parameters, expressed as the maximum effect on a study day and the area under the effect-time curve, characterized the drugs' influence on peripheral neurotransmitter metabolism. The most reliable variables to assess inhibition of MAO-A and -B in humans proved to be DHPG in plasma and serotonin in platelets and MAO-B activity in platelets, respectively. Several variables (DHPG, platelet serotonin) suggested that selegiline has some MAO-A inhibitory activity. This became particularly apparent upon addition of selegiline to moclobemide treatment; i.e., the effects of combined moclobemide and selegiline treatment were statistically greater than those of moclobemide monotreatment. Moclobemide alone exerted a slight inhibition of platelet MAO-B activity. The reported pharmacodynamic interactions are not considered to be clinically relevant. However, due to the previously found supraadditive tyramine potentiation upon simultaneous treatment, moclobemide and selegiline should only be combined when applying dietary restrictions with respect to tyramine.

Resolution, EPC-syntheses, absolute stereochemistry, and pharmacology of the (S)-(+)- and (R)-(-)-isomers of the MAO-A inhibitor tetrindole hydrochloride.

Resolution of (RS)-tetrindole (3) and enantioselective reductions of the imine 7 yielded (S)-(+)-(4) and (R)-(-)-tetrindole (5). The absolute stereochemistry of 4 was established by X-ray analysis of the corresponding Mosher amide 6. From in vitro as well as in vivo data (MAO-inhibition, levels of monoamines and their respective metabolites in rat brain), 4 was identified as the eutomer.

Success rates in producing sympathetic blockade by paratracheal injection.

OBJECTIVE: Cervical paratracheal local anesthetic injections (stellate ganglion blocks) are performed to determine the sympathetic contribution to painful and other conditions of the head, neck, and arm. A block is useful for diagnosis only if the desired physiological effect is confirmed, but the frequency with which sympathetic function is successfully blocked is unclear. The goal of this study is to examine the rates of achieving various endpoints of sympathetic interruption by these injections, using commonly available measures of sympathetic change. DESIGN: Retrospective review. SETTING: Training center. PATIENTS: One hundred unselected consecutive blocks in 40 patients. INTERVENTION: Paratracheal sympathetic block at sixth cervical level. OUTCOME MEASURES: Bilateral hand temperature, ophthalmic changes. RESULTS: Horner's syndrome was successfully produced in 84 blocks and the ipsilateral hand warmed by > or = 1.5 degrees C in 60 blocks. However, the contralateral hand also warmed in 31 blocks so that ipsilateral warming exceeded contralateral warming in only 27 blocks, with diminished success by this criterion when the hand was warm before the block. CONCLUSIONS: We conclude that (a) identifying a Horner's syndrome and ipsilateral warming are not by themselves adequate to confirm selective sympathetic blockade; (b) selective sympathetic blockade of the arm is confirmed only if the temperature increase of the blocked side exceeds that of the contralateral side; and (c) cervical paratracheal blocks frequently fail to produce evidence of sympathetic interruption to the arm. Pathophysiological inferences based on these blocks should be made with caution and only with adequate documentation of physiological evidence of sympathetic blockade.

Radioautographic evidence that the GABAA receptor antagonist SR 95531 is a substrate inhibitor of MAO-A in the rat and human locus coeruleus.

The locus coeruleus (LC), a major noradrenergic nucleus in the brain, probably has a functional role in the regulation of anxiety states as well as vigilance, attention, learning and memory. LC neurons are under the inhibitory control of gamma-aminobutyric acid (GABA) via ionotropic GABAA receptors. However, to date, little is known of the receptor binding characteristics of these neurons. In the present investigation we therefore examined by receptor radioautography the localization of the binding sites for different components of the GABAA receptor complex in the rat and human LC. Both rat and human LC neurons have a high density of binding sites for the pyridazinyl-GABA derivative [3H]SR 95531 (gabazine, a GABAA receptor antagonist for low affinity GABA recognition sites). However, at the concentrations used, no binding sites in the LC were detectable for the benzodiazepine receptor antagonist [3H]flumazenil, the GABAA receptor agonist (for high affinity sites) [3H]muscimol or the ionophore ligand [35S]t-butyl bicyclophosphorothionate (TBPS). Unexpectedly, the pharmacological specificity of [3H]SR 95531 binding to the LC differed markedly from that to most brain regions (IC50 values for GABA and RU 5135 respectively in the LC were > 10(-2) and 10(-3) M; and, for example, in the dentate gyrus the most labelled structure after the LC, 8 x 10(-7) and 1.8 x 10(-9) M). These differences prompted the further characterization of [3H]SR 95531 binding in the LC, revealing a significant affinity for monoamine oxidase type A (MAO-A), which is highly concentrated in this nucleus. In a competition binding study, a reduction of up to 25% of the [3H]SR 95531 binding was observed with MAO-A but not MAO-B inhibitors, at concentrations which produce maximum but selective enzyme inhibition. Correspondingly, 2 h after the oral administration of supramaximal doses of the MAO-A inhibitors moclobemide and Ro 41-1049 (but not the MAO-B inhibitor lazabemide) the in vitro binding of [3H]SR 95531 was markedly reduced (by 77 and 82% of controls respectively). Moreover, enzyme radioautography with [3H]Ro 41-1049 revealed that SR 95531 has a significant affinity for MAO-A (IC50 values were 10(-5) and 4 x 10(-6) M in the LC and dentate gyrus respectively) but not for MAO-B ([3H]lazabemide binding). Altogether, these findings suggest that the high-affinity binding of [3H]SR 95531 to the LC mainly reflects its affinity for MAO-A, which questions its utility as a selective ligand for low-affinity GABA recognition sites in the CNS.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacodynamics of lazabemide, a reversible and selective inhibitor of monoamine oxidase B.

1. The inhibition of monoamine oxidase B (MAO-B) by lazabemide was measured in platelets collected from 35 young (19-36 years) and 40 older (60-78 years) healthy volunteers after single (100-300 mg) and multiple (100-350 mg twice daily) oral doses respectively. 2. The relationship of the effect with plasma concentrations of the MAO-B inhibitor was defined by a sigmoid Imax-model using either a parametric or semi-parametric method for predicting plasma drug concentrations. Population parameter estimates were obtained by the expectation maximization method and a standard two-stage method. 3. At the lowest dose platelet MAO-B activity was almost completely inhibited for around 20 h. No time delay between plasma drug concentration and resulting inhibition of platelet MAO-B occurred. Low concentrations of the inhibitor produced 50% of maximum inhibition (IC50, estimates for population mean +/- s.d.: 0.48 +/- 0.89 microgram l-1 for young and 1.5 +/- 2.3 micrograms l-1 for elderly subjects). The maximum extent of enzyme inhibition attributable to lazabemide (Imax) was 94 +/- 5.1% and 96 +/- 4.5% in the young and older populations. There was no correlation between age and either Imax or IC50. 4. Model parameters describing the interaction of lazabemide with the enzyme did not change over the treatment period of 7 days.

Lazabemide (Ro 19-6327), a reversible and highly sensitive MAO-B inhibitor: preclinical and clinical findings.

Ro 19-6327 (lazabemide, L), MDL 72974, selegiline, AGN 1135 and MDL 72145 were investigated for their MAO inhibitory effect in rat tissues in vitro. The selectivity of MAO-B inhibition of L, selegiline and MDL 72974 was also measured in vitro in human brain tissue as well as ex vivo in rat brain and liver after acute and subchronic administration. Of all compounds investigated L was the most selective for MAO-B inhibition under in vitro and ex vivo conditions. In volunteers, L completely but reversibly inhibited platelet MAO-B with a dose-dependent duration. Clinical trials with L are under way in both Alzheimer's and Parkinson's disease (PD).

Species differences in changes of heart monoamine oxidase activities with age.

It has previously been established that MAO-A activity markedly increases (about 600%) with age in the rat heart. The aim of the present study was to examine the effect of age on the activity of MAO-A and -B in the mouse heart. In contrast to the rat heart, beta-phenylethylamine is deaminated by MAO-B in the mouse heart. Heart MAO-B activity was found to significantly increase (about 70%) with age in both male and female mice, whereas MAO-A activity remained unchanged. Compared to age-matched rats, serotonin-deaminating activity was about 35 times and 204 times lower in young and old mice, respectively.

PDPH in obstetric anesthesia: comparison of 24-gauge Sprotte and 25-gauge Quincke needles and effect of subarachnoid administration of fentanyl.

BACKGROUND AND OBJECTIVES: Postdural puncture headache (PDPH) is a frequent complication of spinal anesthesia. Some investigators have recommended the use of the Sprotte needle to reduce the incidence of this serious complication. This study prospectively compared the incidence of PDPH with two spinal needles of different size and design: the 24-gauge Sprotte (noncutting point) versus the 25-gauge Quincke (diamond, cutting point). The hypothesis that subarachnoid fentanyl will reduce the incidence of PDPH, as suggested in the literature, was also studied. METHODS: Only patients for emergency or elective cesarean delivery were studied. One hundred ninety four patients were randomly assigned to receive spinal anesthesia with one of the two needles (Sprotte, n = 96; Quincke, n = 98). Simultaneously, each patient was assigned to receive hyperbaric 0.75% bupivacaine local anesthetic or a combination of the same concentration of local anesthetic with 20 micrograms of fentanyl (Sprotte with fentanyl, n = 47; Sprotte without fentanyl, n = 49; Quincke with fentanyl, n = 49; Quincke without fentanyl, n = 49). All patients were evaluated during the first 4 postoperative days, and follow-up telephone interviews were conducted 3 weeks after discharge. RESULTS: Four patients (4.2%) in the Sprotte group and seven (7.1%) in the Quincke group developed PDPH. Three out of four patients with headache in the Sprotte and four out of seven in the Quincke group received fentanyl as an adjunct for spinal anesthesia. Two patients in the Sprotte group required an epidural blood patch as a therapy for PDPH. Two patients in the Quincke group had severe headache and required an epidural blood patch. CONCLUSIONS: In the current study, the use of the 24-gauge Sprotte spinal needle resulted in a low incidence of severe PDPH, but was not significantly different when compared with the use of a 25-gauge Quincke needle (oriented parallel to the longitudinal dural fibers). The addition of fentanyl to hyperbaric bupivacaine spinal anesthesia did not reduce the risk of PDPH.

Pharmacology of moclobemide.

Moclobemide is a reversible inhibitor of monoamine oxidase (MAO) with clear preference for the A type (so-called RIMA). The enzyme inhibition shows complex kinetics, and the molecular mechanism of interaction with the enzyme is not yet clear. Moclobemide increases the extracellular concentration of the monoamines in rat brain and decreases the level of their metabolites. Neither a loss nor a cumulation of activity has been observed after chronic treatment. Reversibility of MAO-A inhibition was demonstrated in vitro as well as in vivo. In various animal behavioral models, in particular in a novel model of stress-induced anhedonia, moclobemide was as effective as standard antidepressants. Moclobemide improves cognitive functions that are impaired in experimental situations. A neuroprotective action is seen in rats subjected to transient global ischemia/-hypoxia. Moclobemide lacks anticholinergic and other effects and only slightly increases the pressor effect of orally administered tyramine. Possible links between MAO-A inhibition and the various effects of moclobemide on brain function are discussed.